At the time the Model 16 was introduced to the home computer market, the system represented one of the most advanced personal computers available for a small or home based business.

Classic Home Toys #12 - TRS-80 Part 2

James Russo

Classic Home Toys Installment #12
The Radio Shack TRS-80: The World's First Personal Computer…or was it ? Part II

by James Russo

At the time the Model 16 was introduced to the home computer market, the system represented one of the most advanced personal computers available for a small or home based business.

For Part 1 - Click Here

The Radio Shack TRS-80, long believed to be the world's first home computer, was living up to several of the namesakes that the device had been branded with in the early days of home computing. Many home computer enthusiasts labeled the PC with the unfortunate name of "trash 80" due to a seemingly endless stream of technical problems. The TRS-80 was fraught with software problems, programming errors, hardware drawbacks, and a host of other issues.

Before PC's had a separate monitor peripheral, all home computers of the late 1970's had a self contained monitor (Apple did as well as Early Atari PC's) which was monochrome. The TRS-80 had a white on black display which was a modified RCA XL-100 Black and White television. If one looked closely, the actual color of the system was light bluish. Because of bandwidth problems in the interface card that replaced the TV's tuner, the display would lose horizontal sync if large areas of white were displayed; a simple hardware fix involving less than half an hour's work could be applied to correct that.

Yet another programming glitch involved the system's display of graphics. The video hardware could only display text at 84 or 32 characters wide by 16 lines resolution in upper case. This was because the video memory system used a single kilobyte of video memory. Primitive graphics could be displayed because the upper 64 characters of the 128 character set displayed as a grid of 2X3 blocks (very similar to Teletext). BASIC programs could write directly to the resulting 128X48 grid.

Any access to the screen memory, writing to it using the BASIC statement PRINT or accessing the screen memory directly caused screen "flicker". The bus arbitration logic would block video display while access was given to the CPU causing short black line. Normal BASIC programs would not be much affected by this, but fast programs made in assembly might be badly affected by this effect if the programmer didn't take it into consideration.

The TRS-80 also offered a floppy disk which was an upgrade to the Model I system. The user could add a single density floppy disk interface which was based on a Western Digital 1771 single density floppy disk controller, but the drive lacked a separate "data separator:, and thus was unreliable.

The TRS-80 was the first home computer to run BASIC programming language. There were two versions of the BASIC programming language produced for the Model I Level I BASIC fit in 4KB of ROM and Level II in 12 KB of ROM. The two versions of BASIC available for the Model I were not particularly noteworthy. More impressive was the manual which accompanied the program which was written by David Lien which presented lessons on programming with text and colorful graphics, making the subjects very easy to understand.

Quite a few games were available for the TRS-80 and many leading game programmer and developers wrote games for the TRS-80 based on popular arcade games such as Namco's Pac-Man, Atari's Centipede, and Sega's Zaxxon. Radio Shack had a team of its own programmers designing games specifically intended to work with the TRS-80 limited memory. The TRS-80 was also the first home computer to offer a full suite of office applications including an early spreadsheet VisiCalc and an early word processor Lazy Writer.

Despite the technical problems and drawbacks of the TRS-80, the computer was a popular seller for Radio Shack and developers went back to the drawing board and in the early 1980's released a Model III and later a Model IV. Both version offered significant improvements over the Model I including built-in lower case, a better keyboard, and a faster (2.03 MHz) Z-80 processor. The Model IV also came in a portable version ,an early laptop called the Model 4P.

Radio Shack saw around 1984 that the days of the TRS-80 were limited. By this time, Apple, Atari, and IBM were releasing more sophisticated versions of home computers which would spell doom for the TRS-80. Radio Shack wisely shifted their company focus onto business models of the TRS- version of the TRS-80 called the TRS-80 Model 16 had the ability to run Xenix, Microsoft's version of UNIX.

At the time the Model 16 was introduced to the home computer market, the system represented one of the most advanced personal computers available for a small or home based business. The Model 16 family with Xenix as the operating system became popular with a relatively large library of business and office automation software for its day. Tandy offered multi-user word processing, spreadsheeting, as well as an accounting suite with optional COBOL source for customization. RM-COBOL, Basic, and C were available for programming with Unify and Informix offered as relational databases.

Despite the tremendous improvements made to the TRS-80 family of computers, Radio Shack could no longer stave off heavy competition especially from Apple and IBM. Later versions of Radio Shacks computers, namely the Tandy 1000 systems and follow-ons were marketed by DEC, a joint Tandy and DEC manufacturing venture.

If you are interested in truly experiencing the TRS-80's DOS operating system just like a TRS-80 owner would have back in the 1980's, there are a number of operating system emulators that are available on the internet for download. The files occupy only a few kilobytes of memory and when launched, the TRS-80's DOS appears in a DOS windows which will enlarge to full screen. One of the best TRS-80 emulators available is David Keil's TRS-80/Tandy Computer Emulator page. The emulators can be found at The emulators are freeware, but if you choose to keep them asnd use them, the site webmaster asks for a voluntary $10 donation to help maintain the page and to acquire more software than can be downloaded free of charge.

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